Time-limit relay



G. A. BURNHAIVI.

TIME LIMIT RELAY.

APPLICATION FILED Nov. 22, 1918.

1,402,048, v Patented Jan. 3, 1922,

En... M MIIIIIIIIIL v @WIIIIIIIIII gllIIIIIlIl/K u I.

UNITED STATES PATENT OFFICE.

GEORGE A. BURNHAM, 0F SAUG'US, MASSACHUSETTS, ASSIGNOR T0 SEARS B.

GONDIT, JR., OF BROOKLINE, MASSACHUSETTS. i

TIME-LIMIT RELAY.

j Specification of Letters Patent.

Patented Jan. 3, 1922.

Application led November 22, 1918. Serial No. 263,756.

To all whom t may concern:

Be it known that I, GEORGE A. BURNHAM, a citizen of the United States of America, and residentfof Saugus, in the county of Essex and State of Massachusetts, have invented an Improvement in Time-Limit Relays, of which the following is a specification.

Time limit relays as ordinarily constructed, are divided into three classes; those operating upon a definite or straight line curve regardless of the strength of the overload; those operating upon an inverse curve but in which the time of operation of the device decreases as the strength of the overload increases, and as its name implies, de'- creases in an inverse ratio to the strength of the current; and those operating upon an inverse-definite curve and in which the time 0f operation decreases in an inverse ratio to the strength of the overload up to a certain predetermined strengthof overload and, for overloads in excess of the predetermined value, operates on a definite curve and therefore a fixed time regardless of any further increaseA in value of overload.

T he particular'characteristics that determine the particular curve upon which the relay is adapted to operate are inherent in the relay and determined by its construction and usually cannot be, in any material way, altered without a material change -in its design. It is, in many instances, desirable in a relay to vary the operating characteristic thereof; and so to arrange it that for a definite value of overload the relay will operate to open the circuit at the expiration of a certain time interval; and for another different value of overload to Operate at some other predetermined definite time interval. With a relay so arranged, the operating curve may be varied in any desired manner, and the characteristic of the device may beso altered as to cause it to operate upon a definite curve, an inverse curve, or an inverse-definite curve, or any combinations or variations of these. A time limit device arranged to accomplish the results above set forth constitutes an object of my invention.

A further object of my invention is in the provision of a time limit device so arranged that a plurality'of individual and independent adjustments of the device for different values of overload may be accomplished to cause the device to operate to open the circuit controlled thereby after the expiratlon of a different predetermined time for each adjustment.

Ihe means whereby I accomplish these objects of my invention consists in the provision of a time limit device having a plurallty of independent time elements arranged to be driven preferably from a common source of power; said time elementsl being arranged for independent and selective adjustments of the eriod of time intervening between their initial operation and their control of the circuit associated therewith.A Each independent time element is adapted to be selectively and independently connected to the source of power to be driven thereby, for ythe control of the circuit associated therewith, by independent means governed by the circuit to be controlled and adjustably arranged to be effectively operated to connect its time element with the source of power at values of overload which may be different for each controlling means.

A further object of my invention is in the provision of a switch which is operated by one of the overload responsive means, wheneff'ectively energized, to energize the source of power for the operation of the time element, whereby the time'limit device may be inoperative until upon the occurrences of overloads.

' Fig. l is a diagrammatic representation of a time limit device embodyin my invention.

F ig.' 2 is a detail sectional elevation through one of the time elements with the power driven shaft.

In the drawings, 10 represents the circuit to be controlled by the time limit device and 11 represents an electrically controlled switch or circuit breaker adapted to be opened upon the energization of a control circuit 12 governed by the time limit device.

The time limit device includes a lurality of time elements or discs, of which our, viz. 13, 13a, 13b, and 13c are shown here and it is understood that as many discs may be employed as are desirable. Each disc is provided with a, plurality of holes 14 therein and each disc has an arm as 15, 15'?L 15b and 15, which is pivoted to the disc at its center and extends beyond the periphery thereof and has a pin 16 therein which is adapted to fit within any one of said holes 14: to thereby vary the time period of operstationary stop 18. Said discs 13, 13, 13",`

13 are fixed on the ends of shafts 19, 19", 19", 19 which may be journalled in an upri ht portion 20 on the frame of the machlne. Said shafts 19, 19", 19", 19 may extend through said portion 20, at the other ends thereof, may be provided with bevelled friction wheels, 21, 21", 21", 21 which are positively secured to said shafts whereby said wheels, shafts, and discs are arranged to rotate in unison. A tensile spring 22, (22, 22", 22,) one end of which is secured to a pin 23, (23a, 23", 23) in the upright portion of the frame of the device has its other, and flexible, end wrapped around the hub 24, (24, 24", 24) of the bevelled friction wheel 21 (21, 21", 21) and is secured to a gin 25 (25, 25", 25) extended therefrom.

aid arrangement of spring and wheel form a convenient-means for returning the disc or time element to its normal and un-operatedposition, after the operation thereof.

It is to be understood that the spring illustrated merely furnishes a convenient means for returning the time element to its original ppsition and that an equivalent means may employed where desirable.

A contact pen, as 26, 26", 26" and 26, is provided for each time element and is arranged in the path of movement of the extended arm 15, 15, 15" and 15 thereof. The contact members ofthe pens are adapted to i be moved together when the arm 15, 15, 15"

15, has been moved into contact therewith to complete the switch control circuit 12 to trip the switch or circuit breaker 11 in the circuit 10 to be controlled.

All of the time elements or discs, as 13, 13, 13", 13 are arranged to be independently driven from the shaft 30 which extends in proximity to the bevelled friction wheels 21, 21, 21", 21 of each time element.

Said shaft 30 is driven through the worm gear 31 and worm 32 by the electric motor 33, which is adapted to be energized upon an overload to cause the rotation of the shaft 30. The worm and `worm gear serves las a convenient means for reducing the relatively high speed of the motor to the desired, and relatively low, speed of the time element drive shaft whereby the desired time period may be obtained from any of the time elements or discs driven therefrom. i

A plurality of bevelled friction wheels, 35, 35, 35", 35, one for each disc, 13, 13, 13", 13 are slidably arranged on' said drive shaft 30 adjacent each bevelled friction wheel 21, 21", 21", 21 of the time elements andare arranged to be positively 4driven therefrom by means of the keys 36, 36, 36", 36 ,which per mit a sliding movement of the bevelled friction wheels, 35, 35a, 35", 35 but prevent independent rotation of said wheels and shaft. Each of the bevelled wheels 35, 35, 35", 35 is normally arran ed to be disconnected, or independent, from its co-acting bevelled wheel associated with the individual time elements but is adapted to be moved into engagement therewith so that the bevelled face thereof is forced into engagement with the bevelled face of its co-acting wheel whereby the rotation of the drive shaft 30 is transmitted to the discs 13, 13, 13", 13 to cause its rotation. It is to be understood that the friction drive, as shown by the `coacting bevelled wheels is merely illustrative of one means by which the connection between the individual time elements and the common drive shaft may be arranged and it is obvious that many other means suggest themselves, any Aof which may be employed under suitable and desirable circumstances. Y It is seen that, .when said shaft 30 is ro-l tating and a bevelled friction wheel as 35 is away from contact `with its corresponding bevelled wheel'as 21 of a time' element, the time element will not be driven from. the shaft but, when said bevelled friction wheel as 35 is moved vinto engagement with its coacting wheel at 21, the time element or disc associated therewith will be frictionally driven to eventually operate to close the control circuit after the expiration of a deiinite time.

A plurality of electro-magnets 40, 40", 40", 40 are employed to control the rotation of the discs, one for each time element, and all are adapted to be energized from lthe circuit 10 to be controlled, either by a transformer 41 as shown, or by means so arranged that the energization of said coils is proportional to the energization of the circuit 10.

Each of said electro-magnets, 40, 40", 40", 40 is provided with an armature as 42, 42", 42", 42 which is secured to one end of a lever, 43, 43", 43", 43 'which may be pivoted to a post 44, 44", 44",44 extended from a portion 20 of the frame of the device. levers 43, 43a, 43", 43 are extended upwardly .from said electro-magnets and terminate in Said gage with o-r ibe disengaged from its correspending friction wheel associated with theseparate time elements.

A, retractile Spring as 50, 50, 50", 50 is connected to each lever 43, 43, 43", 43 and serves normally to pull said, levers against' a stop as 51, 51a, 51", 51a, and thereby normally maintain the friction wheels 35, 35,

35h, 35c away from engagement with the a correspondin friction wheels ofthe time elements, and t e arma-tures 42, 42a, 42", 42, away from the cores of the electro-magnet 40, 40a, 40h, 40G.

The lever 43, associated with electro-magnet 40 which is adapted to be effectively energized upon the smallest excess current flow, is provided with an extended arm 52 to which is secured a movable switch member or brush 53. Upon sufficient energization of said electro-magnet 40 said member 53 is moved into contact with the stationary switch blocks 54, and 54 in the motor circuit 55 to thereby energize said circuit to cause the rotation of shaft 30. It may be seen that upon the sufiicient energization of any one of said electro-magnets, 40, 40a, 40, 40, the friction wheel associated therewith will be moved into Contact with the co-acting friction wheel of a time element to thereby cause said time element to be driven from the common drive shaft 30. In the operation 'of the device as illustrated and above described each electro-magnet 40, 40a, 40h, 40c is adjusted as by varying the tension of its spring 50, 50a, 50h, 50c to be effectively energized to move its corresponding lever 43, 43a, 43h, 43c at different values of current. Normally, the motor 33 is unenergized and therefore the drive shaft of the device is without rotation. Upon a current flow in circuit of sufiicient value to effectively energize said electro-magnet 40, the armature of said electro-magnet is attracted and the lever 43 is moved to close either the switch 53 or the motor circuit 55 and the motor is consequently energized to rotate the drive shaft 30. At the same time, lever 43 operates to move the friction wheel 35 associated therewith along the drive shaft 30 and into engagement with the co-acting friction wheel associated with the time disc 13 and said disc consequently is set in rotation to move its arm on said disc 13 and the circuit 12 is thereby energized to open the switch 11 and thereby interrupt the circuit 10.

The adjustment of the other electro-magnets 40a, 40, 40, is adapted to be greater than the adjustment of said electro-magnet 40 and, if the strength of the current in circuit 10 to be controlled does not greatly exceed the value for which the electro. magnet 40 is adapted to operate, said other electromagnets will remain ineffectively energized and consequently the time elements associated with said electro-magnets will remain unoperated and the initial time element 13 will alone be effective in causing the openin of the circuit 10 to be controlled.

pon an overload of sufficient strength to 65 cause the effective energizaton of another of said electro-magnets, as 40, for instance, the time disc 13a will bewcaused to rotate to eventually cause the contact pens 26a to be brought into contact to also close the switch control circuit. Upon increasingly greater values of overload, the electro-magnets 40, 40h, 40C, will be progressively effectively energized to also cause the closing of the circuit 12. Normally the initial time element, or the one with which the motor `control switch 53 is associated, is adjusted to give the longest time period of any of the time elements of the device. If the overload value is suflicient to cause the simultaneous effective energization of two electro-magnets, as the initial `magnet 40 and another magnet as 40, both discs 13 and 13a will be simultaneously set in rotation and, as the setting of the arm 15 of the disc 13 is usually such as to provide a longer time period of operation than the setting of arm 15a of the disc 13, said second time element will operate to close the circuit 12 before the arm 15 of the first time element has sufiiciently rotated, and the second time element will therefore be the one which causes the opening of the circuit 10 to be controlled. If, however, the overload was, initially, only suficient to cause the effective energization of the first time element, and after said time element had been in operation for a time less than that'necessary for it to cause the opening of the switch 11, the overload subsequentlyincreased to such a value as to cause the effective energization of an electro-magnet of a second 100 time element as 40a, then it may be the first time elelnent will be effective in causing the interruption of the circuit 10 rather than the second time element, or it may be that the second time element will be effective to cause 105 the interruption of' the circuit 10, and the particular time element which is effective to cause the opening of switch 12, depends upon the elapsed period of time between the effective energization of the electro-magnets of 110 the two time elements and upon the relative settings of the arms 15 and 15a of said time elements. The other time elements of the device operate in 'a similar manner upon an overload of sufficient value t0 efiectively en- 115 crglze the electro-magnets associated therewit- It may be seen that the device may be adjusted to operate upon a definite or straight line curve by setting all of the ltime discs 13 to close their Lcontact pens at the same time, as by placing the arms 15, 15a, 15b, 15c at the same relative positions on said discs. The device may also be adapted to operate upon an approximate inverse-definite curve by setting, say, the disc 13a to effectively operate at a shorter time than the disc 13 and setting thediscs13b and 13c to simultaneously operate after the expiration of the same time or by having one disc which is responsive to all over-loads in excess of a predetermined value. The device may, further, be adjusted, to operate upon an inverse curve by arranging the time discs to effectively operate at progressively decreasing intervals of time; and the adjustment of the v-rality of independent time elements eachv of which is independently adjustable for the timed control of a common circuit, means governed bythe circuit to be controlled to govern the operation of said time elements and .a common driving means for said elements.

2. A time limit device comprising a plurality of time elements, a common source of power therefor, and means governed by a clrcuit to be controlled for independently connecting said time elements to the source of power to be driven thereby.

3. A time limit device including a plu'- rality of independent time elements, a plurality of current responsive means governing the operation of said elements, and a common driving means for said elements.

4. A time limit device including a plurality of independent time elements, a common driving means therefor, said elements normally in pendent of said driving means, and a lplurality of current responsive means governingthe connection between said time elements and drivin means.

Y 5. A time limit evice including a plurality of independent time elements, a common driving means therefor, said elements normally independent from said ,driving means, and a plurality-of current responsive means adapted to be 'effectively energized at differing values ofoverload to govern the connectlon between the time elements and the driving means for the control of an electric circuit.

6. A time limit means including a plurality of independent time elements, a common drivin means therefor, said elements normally disconnected from said driving means, clutching means adapted toindividually connect each time element with said drlving means, and current responsive means to control the clutchin means.

7 A time limit device inclu ing a plurality of time elements, a common driving means therefor, said elements normally disconnected from said driving means, individual clutchin means for each element 60 for driving said e ements from said driving means, and current responsive means adapted to be 'effectively energized at differing current values to control the clutching means.l

8. A time limit device including a pluralit of time elements arran ed to fbe indivi ually adjusted for the tlmed control of an electric circuit, a common driving nieans therefor, clutching means to individually connect each time element with said driving means to -be driven thereby, and a' current responsive means for each time element,l each responsive means arranged to be individually adjusted for the current value at which they are effectively energized,

d each responsive means arrangedto control its associated clutching means.

9. A time limit device including aplurality of time elements, a common driving4 80 means therefor, said means being normally unoperated, a plurality of current responsive means controlling the operation of the time elements, and means associated with one of said responsive means to control the operation of the driving means.

10. A time limit device including a plurality of time elements, a common driving means therefor, said means being normally unoperated, a plurality of current responsive means controlling' the operation of the time elements, said responsive means selectively responsive to diiiering values of current, and means to control the operation of the driving means associated with the-,96 means responsive to the smallest value ofY current.

In testimony whereof, I have signed my name to this specification, in the presence of two ,subscribin witnesses.

' EORGE A. BURNHAM. Witnesses:

. T. T. GREENWOOD,

H. B. DAVIS. 

